Appleton, Sir Edward Victor

SUBJECT AREA: Broadcasting, Telecommunications

[br]

b. 6 September 1892 Bradford, England

d. 21 April 1965 Edinburgh, Scotland

[br]

English physicist awarded the Nobel Prize for Physics for his discovery of the ionospheric layer, named after him, which is an efficient reflector of short radio waves, thereby making possible long-distance radio communication.

[br]

After early ambitions to become a professional cricketer, Appleton went to St John's College, Cambridge, where he studied under J.J.Thompson and Ernest Rutherford. His academic career interrupted by the First World War, he served as a captain in the Royal Engineers, carrying out investigations into the propagation and fading of radio signals. After the war he joined the Cavendish Laboratory, Cambridge, as a demonstrator in 1920, and in 1924 he moved to King's College, London, as Wheatstone Professor of Physics.

In the following decade he contributed to developments in valve oscillators (in particular, the "squegging" oscillator, which formed the basis of the first hard-valve time-base) and gained international recognition for research into electromagnetic-wave propagation. His most important contribution was to confirm the existence of a conducting ionospheric layer in the upper atmosphere capable of reflecting radio waves, which had been predicted almost simultaneously by Heaviside and Kennelly in 1902. This he did by persuading the BBC in 1924 to vary the frequency of their Bournemouth transmitter, and he then measured the signal received at Cambridge. By comparing the direct and reflected rays and the daily variation he was able to deduce that the Kennelly- Heaviside (the so-called E-layer) was at a height of about 60 miles (97 km) above the earth and that there was a further layer (the Appleton or F-layer) at about 150 miles (240 km), the latter being an efficient reflector of the shorter radio waves that penetrated the lower layers. During the period 1927–32 and aided by Hartree, he established a magneto-ionic theory to explain the existence of the ionosphere. He was instrumental in obtaining agreement for international co-operation for ionospheric and other measurements in the form of the Second Polar Year (1932–3) and, much later, the International Geophysical Year (1957–8). For all this work, which made it possible to forecast the optimum frequencies for long-distance short-wave communication as a function of the location of transmitter and receiver and of the time of day and year, in 1947 he was awarded the Nobel Prize for Physics.

He returned to Cambridge as Jacksonian Professor of Natural Philosophy in 1939, and with M.F. Barnett he investigated the possible use of radio waves for radio-location of aircraft. In 1939 he became Secretary of the Government Department of Scientific and Industrial Research, a post he held for ten years. During the Second World War he contributed to the development of both radar and the atomic bomb, and subsequently served on government committees concerned with the use of atomic energy (which led to the establishment of Harwell) and with scientific staff.

[br]

Principal Honours and Distinctions

Knighted (KCB 1941, GBE 1946). Nobel Prize for Physics 1947. FRS 1927. Vice- President, American Institute of Electrical Engineers 1932. Royal Society Hughes Medal 1933. Institute of Electrical Engineers Faraday Medal 1946. Vice-Chancellor, Edinburgh University 1947. Institution of Civil Engineers Ewing Medal 1949. Royal Medallist 1950. Institute of Electrical and Electronics Engineers Medal of Honour 1962. President, British Association 1953. President, Radio Industry Council 1955–7. Légion d'honneur. LLD University of St Andrews 1947.

Bibliography

1925, joint paper with Barnett, Nature 115:333 (reports Appleton's studies of the ionosphere).

1928, "Some notes of wireless methods of investigating the electrical structure of the upper atmosphere", Proceedings of the Physical Society 41(Part III):43. 1932, Thermionic Vacuum Tubes and Their Applications (his work on valves).

1947, "The investigation and forecasting of ionospheric conditions", Journal of the

Institution of Electrical Engineers 94, Part IIIA: 186 (a review of British work on the exploration of the ionosphere).

with J.F.Herd \& R.A.Watson-Watt, British patent no. 235,254 (squegging oscillator).

Further Reading

Who Was Who, 1961–70 1972, VI, London: A. \& C.Black (for fuller details of honours). R.Clark, 1971, Sir Edward Appleton, Pergamon (biography).

J.Jewkes, D.Sawers \& R.Stillerman, 1958, The Sources of Invention.

KF